I only had experience with gooseneck hitches on my equipment trailers. When I bought a 5th wheel RV, I converted it to a gooseneck hitch. My RV in not too heavy (only 26' long) and I have had no problems with it. However, I thought that I should mention one potential problem.
Since a 5th wheel hitch limits side to side tilting to around 10 - 15 degrees, the RV body (which is wider than the truck bed) can usually not touch the truck bed sides. With the almost unlimited side-to side tilting of a gooseneck, the RV body can touch and damage your truck in certain situations. I will try to describe one such situation:
Approaching an uphill "T" intersection with another road. The 2nd road is tilted away from Road #1 (due to elevation of the lanes in a curve, for example). Your truck turns onto Road #2 while the RV is still sloped along Road #1 and the RV will hit the truck bed sides. While hard to describe without using my hands, this happened to me a couple of times.
That's an excellent point I had never thought of or seen mentioned.